Paddle Wheel Flow Meter Basics
The paddle wheel rotor, body, and display/controller make up the basic components of paddle wheel flow meters. Paddle wheel flow meters measure fluid volume and volumetric flow. The paddle wheel sensor is made up of a roto or impeller that can freely revolve around a rotor pin. The rotor or paddle has magnets embedded into the ends. This rotor impeller is positioned in a direction that is perpendicular to the flow of the medium and will rotate once it is placed in the medium.
The Operating Theory Behind Paddle Wheel Flow Meters
As the fluid moves a frequency output voltage signal that is proportionate to the flow rate is generated by the paddle wheel meter as the magnets in the blades of the device spin past the sensor. The frequency and voltage output will both increase in direct proportion to the rate of flow.
There are two different installation types when it comes to paddle wheel meters. The paddle wheel flow meter can be installed “in-line” or “insertion style” into a pipe fitting. The Truflo® TK series paddle wheel flow meters are available in PVC, PP, PVDF, and 316SS materials.
It is industry practice to ensure that a minimum run of straight pipe must be present both before 5x pipe diameter and after the sensor 3x pipe diameter in order for a paddle wheel meter to function within the desired accuracy range. This requirement is shared with turbine meters.
The signal from the paddle wheel meter can be read locally right on the flow meter or the signal can be transmitted to a remote display. The TK and TI series paddle wheel flow meters indicate flow rate and flow total.
The output signal that has been processed can be utilized in a variety of ways, including regulating the process, producing an alarm, and transmitting signals to the external display or valve.
In many flow system applications, particularly those dealing with water or fluids with similar properties to water, paddle wheel flow meters, provide an option that is both reasonably inexpensive and highly accurate.
Advantages of Using a Paddle Wheel Flow Meter
• Low-cost solution that provides excellent precision
• Very easy to install and maintain, resulting in a low total cost of ownership
• Virtually no pressure drop making it perfect for gravity flows, or low flow applications
• The insertion flow meter design reduces the cost of flow measurement in larger sizes, and reduces both the cost of installation and the cost of maintenance
The Constraints of Using a Paddle Wheel Flow Meter
• Paddlewheel meters may not function properly with high-viscosity fluids where the flow profile is laminar.
Paddlewheel meters work best with clean fluids because particulates can prevent the paddle from spinning properly.
• Not suitable for gases.
• Requires a turbulent flow profile (consistent fluid velocity across the pipe diameter) for accuracy.
• Requires a straight run of pipe before and after the flow meter to allow swirl patterns in the flow stream to dissipate.
Typical uses for paddle wheel flow meters include the accurate measurement of preset fluid quantities in dispensing systems, regulation of chemical metering pump output, flow verification, irrigation systems, and alerting users to flow rate increases or drops outside a predetermined range.
Please contact us to discuss your application
